LB films incorporating the J-aggregate of cyanine dyes, N, N'-dioctadecyl-oxacyanine perchlorate (S9) and N, N'-dioctadecyl-thiacyanine perchlorate (S11), were prepared by using octadecane as the matrix molecule. Fluorescence spectra of the LB films were measured in wide temperature range. Fluorescence intensity and its peak position of S9 and S 11 depend on temperature. In low temperature fluorescence spectra of S9 and Sll J-aggregates, a broad peak appeared whose position is located at longer wavelength than that of resonance fluorescence. The increase of fluorescence intensity was observed at low temperatures. These effects were also observed for the S9 + S11 mixed aggregate.